University Calculus: Early Transcendentals (3rd Edition)

Published by Pearson
ISBN 10: 0321999584
ISBN 13: 978-0-32199-958-0

Chapter 11 - Section 11.1 - Three-Dimensional Coordinate Systems - Exercises - Page 600: 34

Answer

$x^{2}+y^{2}=3,\quad z=0$

Work Step by Step

The distance from $(0,0,1)$ to$ (x,y,z)=2$ is: $\sqrt{x^{2}+y^{2}+(z-1)^{2}}=2$ The distance from $(0,0,-1)$ to $(x,y,z)=2$ is: $\sqrt{x^{2}+y^{2}+(z+1)^{2}}=2$ The distances are equal, so we equate the LHS's $\sqrt{x^{2}+y^{2}+(z-1)^{2}}=\sqrt{x^{2}+y^{2}+(z+1)^{2}}\quad$ Square both sides: $ x^{2}+y^{2}+(z-1)^{2}=x^{2}+y^{2}+(z+1)^{2}\quad$ Simplify: $(z-1)^{2}=(z+1)^{2}$ $z^{2}-2z+1=z^{2}+2z+1$ $-4z=0$ $z=0$ This set of points is in the xy-plane. Substitute $z=0$ in $x^{2}+y^{2}+(z-1)^{2}=4,$ $x^{2}+y^{2}+1=4,\quad z=0$ $x^{2}+y^{2}=3,\quad z=0$ We get a circle of radius $\sqrt{3}$ in the xy-plane, centered at the origin.
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